Some of image forming apparatuses, such as electrophotographic copiers and printers, include a printer head that includes an LED chip operable to emit light and a lens for forming an image in a predetermined position by using light emitted from the LED chip. In such an image forming apparatus, in order to form an exposed image as fine as possible on the surface of an electrophotographic photosensitive member, the surface of the electrophotographic photosensitive member has to be precisely aligned with the position where an image by using light from the optical printer head is formed. For example, Japanese Unexamined Patent Application Publication No. 7-195735 discloses an optical printer head including a mechanism for precisely aligning with the surface of an electrophotographic photosensitive member with a position where an image is formed by using light through a lens. The optical printer head disclosed in Japanese Unexamined Patent Application Publication No. 7-195735 includes, on the side of the optical printer head, pin-shaped projections projecting in the direction in which light from a light-emitting device travels. The projections come into contact with a reference member on the side of an image forming apparatus, so that the optical printer head is positioned in the image forming apparatus.
In the optical printer head disclosed in Japanese Unexamined Patent Application Publication No. 7-195735, however, the positioning pins are fixed to, for example, a base or heatsink on which a substrate provided with the LED chip is mounted. In the case of the optical printer head disclosed in Japanese Unexamined Patent Application Publication No. 7-195735, the pins have to be fixed outside a substrate mounting area in the base or heatsink. As thus the base or heatsink is relatively large, the size of the optical printer head is also relatively large.
In consideration of the above-described problem, it is an object of the present invention to provide a simple-structured optical printer head capable of setting both of the position of a light-emitting device in an image forming apparatus and the position of a lens array in the image forming apparatus with relatively high accuracy, and an image forming apparatus.